The present invention relates to an optical-fiber coupling device for coupling to an optical operation device an optical fiber for permitting input or output of optical information.
When it is desired to construct an optical transmission system, it becomes necessary to use various optical operation devices such as an optical coupler for causing an optical branching or merging, an optical switch for switching an optical transmission line, an optical multi/demultiplexer for effecting optical wavelength division multiplexing transmission, etc., as well as an optical transmitter and optical receiver. For permitting input or output of optical information, thereby permitting the transmission of this information, an optical fiber is used in these devices. The connecting or coupling of the optical fiber to the optical operation devices is effected by the use of various methods. For example, Japanese Patent Disclosure (Kokai) No. 53-55134 discloses a fiber coupling device having a rod lens and an optical fiber. In this case, a resilient member is used for coupling the optical fiber to the rod lens. Japanese Patent Disclosure (Kokai) No. 55-15184 discloses an optical-fiber coupler unit wherein a light incident end face of the optical fiber and a glass plate are fixed to each other by means of an epoxy resin having a refractive index substantially equal to that of the optical fiber and glass plate. Further, Japanese Patent Disclosure (Kokai) No. 56-147111 discloses an optical-fiber connector unit with a fiber-side connector element to which an optical fiber is fixed, and an element-side connector element to which an optical receiving element is fixed, both said connector elements being detachable. In this case, as seen, a pair of connectors are used for coupling the rod lens and the optical fiber.
In the above-mentioned prior art optical-fiber coupling unit, respective axes of the optical fiber and the optical operation device are very likely to be misaligned due to mechanical or thermal displacements of the coupling members, used for coupling the optical fiber, and the members to be connected. This axial misalignment causes optical loss and, at the same time, deteriorates the fiber-insertion loss characteristic (optical loss due to insertion of the optical fiber) of the optical-operation device. Besides, this axial misalignment also raises the problem of decreasing the mechanical stability of the coupling unit.